Biomass/Production Outline Definition & uses of production Methodsto measure production Advantages & disadvantages of production for production Calculating & analyzing production Definitions of ProducTION Production - amount of carbon fixed from CO 2 to organic material in an area (mass/area) Biomass - total weight of living organisms Phytomass - total weight of plant biomass Standing crop - biomass in an area at one point in time Peak standing crop - highest value for standing crop within a year (varies with species) Definitions of ProducTIVITY Primary productivity - rate of C fixation (accumulated biomass) in an area per unit time (mass/area/time) Gross primary productivity (GPP) - total amount of energy (carbon) fixed by photosynthesis per unit time (total production) Net primary productivity (NPP) - GPP minus losses by respiration (net production) Belowground NPP Annual net primary productivity (ANPP) - NPP on a per year basis More Terms Related to Production Herbage - production of herbaceous plants Browse-production of woody plants used by browsing animals Forage - production of herbaceous and woody plants used by foraging/grazing animals Uses of Production Scientific studies - Carbon storage Energy budgets (carbon flux) Indicator of ecological dominance Indicator of plant vigor Management - Grazing capacity/stocking rates Range condition Wildlife habitat 1
Direct Harvest Clip to ground level Clip species or functional groups? Current season s growth vs. total growth? Rooted vs. canopied plants? Separate out live vs. dead? Dry @ 60-70 C for 24-48 hours Weigh Biomass (above vs. below vs. total) % dry matter = dry wt./fresh wt. * 100 1. Double weight sampling Estimate biomass in several plots Clip representative plots and assign biomass estimates Re-estimate biomass of plots 2. Weight unit estimate Define unit of vegetation Count the # of units Determine dry weight of one unit Multiply for whole plant biomass 3. Comparative yield technique Select five plots that cover range of biomass Rank all plots relative to five reference plots Clip and weigh representative plots and assign biomass values 3. Plant dimensions Measure canopy widths and plant height to calculate volume Harvest representative size classes and establish a regression to estimate biomass Dimensional Analysis Species 1 Biomass Species 2 Species 3 Volume Ludwig et al. 1975 2
Shoot Growth DBH in Trees Digital Imagery Remote Sensing Aerial photograph (6/27/01) of MGCF plots; access paths and crust disturbance treatment are visible. Remote Sensing Belowground NPP Minirhizotrons In this Landsat Image of Las Vegas and Lake Mead, vegetation appears as a green color NDVI image of a basin in NV, colors highlight areas of higher vegetation density 3
Belowground NPP Minirhizotrons NPP Eddy Covariance Domes Measure net ecosystem exchange (NEE) net CO 2 in and out of ecosystem Advantages of Production Good indicator of ecological dominance Intuitive and easy to visualize Easy to measure Disadvantages of Production Destructively sampled (mostly) Not practical to get belowground production Many species reach peak production at different times Time and labor intensive for Production Define attribute measured Time scale per year or over many years Aboveground vs. belowground vs. total Standing crop vs. peak standing crop Moisture content varies Always compare production on dry weight basis Calculating of Production Depends on Method!!!!! 4
Analyzing Production Sampling Unit Sample Independence Plots repeated measures Transects repeated measures 5